Process for producing power



July 20, 1965 D. R. STERN ETAI. 3,195,304 T PROCESS FOR PRODUCING POWER original Filed July 16, 1962 2 Sheets-Sheet 1 THE SYSTEM SODlUM-POTASSIUM-CESIUM FIG-l DAVID R. STERN ROBERT D. STEWART INVENTORS BY Mm ATTORNEY July 20, 1965 D. R. STERN ETAL 3,195,304

PROCESS FOR PRODUCING POWER Original Filed July 16, 1962 2 Sheets-Sheet 2 coNDENsER SUPERHEATER POWER PRODUCING MEANS FlGr-Z CONDENSER POWER PRODUCI NG MEANS FRACTIONATOR ATOMIC REACTOR AVID R STERN D ROBERT D. STEWART INVENTORS ATTORNEY FIG-3 melting points an an inert environment.

United States Patent O 3,195,304 PROCESS FOR PRODUCING POWER David R. Stern, Fullerton, and Robert D. Stewart, La

Habra, Calif., assignors to American Potash & Chemical Corporation, Los Angeles, Calif., a corporation of Delaware Griginal application July 16, 1962, Ser. No. 209,864. Divided and this application May 1, 1964, Ser. No. 368,439

4 Claims. (Cl. S0-36) This application is a division of application Serial No. 209,864, tiled July 16, 1962, for Process and Product.

This invention relates to alkali metal alloys and to their methods of preparation. In particular, this invention relates to ternary cesium=potassium=sodium alloys and their methods of preparation.

Low melting, non-aqueous liquid heat transfer media which are liquid over a Wide range of temperatures have long een sought. The present ternary alkali metal alloys provide a non-aqueous heat transfer medium which is liquid from about 73 C. to about 740 C. under atmospheric pressure. This alloy enjoys wide application in heat transfer, power cycles and in other applications where a heat carrying medium which is liquid over a wide temperature range is necessary. The present liquid ternary alloys are possessed of certain physical properties, for example, high heat capacity and thermal conductivity, which properties enhance the value of these alloys for use as heat carrying fluids in many applications.

Broadly, these alloys are comprised of a major amount of cesium, a minor amount of potassium and a small amount of sodium.

More particularly, ternary alloys of this invention,

v contain by weight from about 2 to about 7% sodium,

from about 16 to about 36% potassium and from about 60 to about 80% cesium. Alloys falling within this range of composition are liquid down to at least about 60 C. Between about 60 C. and about 73 C., a small amount of solid phase may appear in the liquid. The eutectic composition has a melting point of about 73 C.

Preferably, the alloys of this invention will contain from about 2.5 to about 4.5% sodium and from about 2O to about 31% potassium and from about 65 to about 77% cesium. These preferred alloys are liquid down to a temperature of at least about 70 C. Below this temperature down to about 73 C., most of the preferred alloy remains liquid but some solid phase is present.

Particularly, preferred alloys are those having the composition of about 2.8% to about 3.2% sodium and from about 20% to about 30% potassium and from about 67% to about 77% cesium. These preferred alloys are completely liquid down to a temperature of at least about 70 C. Our most preferred alloy is that falling within the range of composition of about 70-77% cesium, about 22.5-25.5% potassium and about 2.9-3.l% sodium. This alloy has a composition very close tothe eutectic point and is substantially liquid down to a temperature of about 73 C.

The alloys of this invention are prepared by mechanically mixing these metals at a temperature above their Mixing can be accomplished by agitation, stirring, or other conventional mechanical mixing procedures. Typical inert environments include anhydrous mineral oil or inert gas such as argon, neon, or the like.

FIG. 1 illustrates the phase diagram for the alloys of this invention.

3,195,304 Patented July 20, '1965 FIG. 2 illustrates schematically one preferred embodiment for producing energy according to this invention.

FIG. 3 illustrates schematically an alternative embodiment for producing energy according to this invention.

Referring specifically to FIG. l, the area bounded by line ABCDA contains the most preferred alloys according to this invention. The alloys having approximately the composition of point A have a melting point between about 72 C. and 73 C. Alloys having the approximate composition of points B, C, and D have melting points of about C. Alloys having a composition falling on line EFGHE have a melting point of approximately 60 C. Alloys having a composition falling within the area bounded by line EFGHE and outside the area bounded by ABCDA, have a melting point between about 60 C. and about 70 C.

Alloys having the composition of this invention are particularly useful in applications wherein it is necessary to store a heat transfer medium under conditions in which it is undesirable or impossible to maintain the storage receptacle in a heated condition. Such conditions occur in many systems, for example, in aircraft and missile applications.

Referring speciiically to FIG. 2, which exemplifies one specific application of the alloys of this invention in producing power, an alkali metal alloy of this invention is with-drawn from a mixed metal storage receptacle 10 through a conduit 12 by pump means 14 and is transferred to a fractionator 16 and thence to a boiler 18. In boiler 18, heat from a source 26 is supplied to the alkali metal alloy of this invention. Heat source 26 can be connected to any heat generating source such as steam or molten sodium from an atomic reactor. The alloy of this invention is heated in boiler 18 to the boiling point of cesium (670 C.) whereupon cesium rich vapor is distilled out of boiler 18 upward into fractionator 16. The residue of cesium-lean sodium and potassium left in boiler 18 is conducted by means of a conduit 20 to a mixer 22.

A cesium vapor stream is conducted from fractionator 16 by means of a conduit 24 to a super heater 25. The cesium vapor is supplied with any additional heat as may berequired in the super heater 25.v If additional lheating is not required, super heater 25 can be omitted. The cesium vapor is then conducted by means of a conduit 2S to a power producing means 30 wherein the cesium vapor expends a portion of its energy in the production of power. Any suitable power producing means including, for example, a turbine can be used to produce power. Conventional turbines known to the are are suitable for this purpose. Cesium vapor is expelled through power producing means 30 and is conveyed by means of a conduit 32 to a condenser 34 wherein the cesium vapor is condensed to liquid cesium. Any suitable condensing means can be employed at this stage, it only being necessary that the particular condenser be capable of condensing substantially all of the cesium vapor chosen to cesium liquid. Y

In mixer 22, the liquid residue of sodium and potassium from conduit 20 is mixed with the liquid cesium from conduit 36 to form the alloy of this invention in the mixer 22. The alloy of this invention is lthen conveyed lby mean-s o-f conduit 38 to receptacle 10 for storage prior to reuse in the cycle.

In operating the equipment illustrated iby FIG. 2, the

l rate of liquid residue supplied to mixer 22 through conduit 20 and the rate of liquid cesium supplied to mixer 22 through conduit 36 are regulated so that the proper proportions of cesium, sodium and potassium are present in mixer 22 to constitute an alloy of this invention.

The compositions of this invention can be employed cheeses advantageously in a power producing cycle wherein` the composition and its individual constituents are the only heat transfer media employed in the entirek power generating system.

The following table contains pertinent thermodynamic data comparing .the properties of typical alloys of'this invention with the properties of sodium, potassium,

v cesium, mercury and various binary mixtures.

One advantageous power generating system in which These data rshow that the alloys of this invention have the compositions of this invention can be employed as an extremely low melting point anda very high boiling the sole heat transfer medium is that illustrated in FIG. point. The other physical properties of Ythese alloys 3 render them much more desirable and generally superior Accordig to the prcccss schematically Shown in F1G- to single metals or binary mixtures for use as heat trans- 3, a fractionator 40 is supplied by a conduit i2V with a 10 fsf medialiquid binary alkali metal mixture of sodium and potas- The alkali metals used to prepare `the alloys of this sium. This bin-ary mixture has been heated almost to invention are lcommercially available." These commerits boiling point under the pressure of the system by cially available alkali metals are of adequate purity for passage through atomic reactor 44. Inboiler 46, this use in this invention. binary mixture is contacted with a cesium rich composi- The use of cesium `in the production lof power by OII Supplied through a Conduit 4S- FraCOIlatOr 40 and means of extracting power from cesium vapor has many boiler 46 operate to separate the cesium from the sodium advantages. In manyy applications such as, for example, and potassium. The cesium leaves the fractionator 40 i high temperature nuclear applications, it is necessary to as a vapor which is conducted through a conduit 50' to use liquid metals since these are the only materials which a power producing means 52. In power producing means are adequately stable under these conditions. VAlkali 52, the excess energy contained within the cesium rich metals are useful in these applications because they have vapor is expended to produce power by a conventional relatively low melting and boiling points and are liquid means as, for example, a turbine, a magnetohydrodynarnover wide temperature ranges. For many applications, ic generator or combinations of these, and the like. cesium is particularly desirable because of its very low Cesium rich vapor is then conducted ythrough a conduit melting point of 28.5 C. This low melting point means 54 to a condenser 56 wherein -the cesium is condensed that when cesium is present in its liquid state, excessive to` its liquid state. The condensed cesium rich liquid heat need not be applied to the cesium to keep it liquid. is then returned through a conduit i8 and fractionator Also, if the cesium is inadvertently allowed to solidify 40 to boiler 46. Portions or all of this system can be. in theapparatug it can be rendered molten again withplaced under either positive or negative pressure, With out the application of large quantities of heat. respect to atmospheric pressure, as is desired to achieve Cesium has many desirable physical properties which adequate material and energy balances. maize it valuable for use in the production of power. For

It is necessary to avoid the circulation of any subexample, it has a low density and a low heat of vaporizastantial amount of cesium through an atomic reactor betion.. It is often desirable to operate the power produccause cesium has a relatively high neutron cross section. :ing process of this invention in such a manner that the Sodium and optassium, on the other hand, can be cirinitial ternary mixture which is supplied :to the boiler is culated through an katom-ic reactor without difficulty besomewhat richer in cesium than those compositions indicause they possess relatively low neutron cross sections. cated above to be the preferred compositions. When the If it is desired to use kthis lluid as a moderator within ternary mixtures of this invention are heated and fracthe reactor, an amount of `cesium proportional to the tionated to provide cesium vapor for use in producing amount of moderation desired can be circulated ywith power, if the initial starting composition is rich in cesium, the sodium and potassium. the vapor which is evolved from the boiler will be sub- In the specification, claims and Vspeeilic examples, all stantially pure cesium. Under these conditions, the resiparts and percentages are by weight unless otherwise due left in the boilerwill be a composition which is close indicated. to the area defined by line ABCDA in FIG. l and will In a typical preparation of the eutectic alloy of this inthus enjoy the advantagesof `a low melting point. In vention, molten cesium, potassium and lsodium yare mixed this manner, it is possible to optimize both the advantages under an inert atmosphere of argon to produce an alof using a substantially pure cesium vapor and developing loy having the composition 3.02% sodium, 21.55% potasa residue with a very low melting point.y sium and 75.43% cesium, MP., -72.4 C. 50 The equipment utilized in the power producing process T able I Na-K-Cs Alloy Physical Property 100% K 100% Na 100% Cs 100% Hg 77% K, 23% K, 5% Na, 23%Na 77%Cs 95%Cs f PointA PointA PointI-l Mening Point o.) 63.7 97.8 28.5 38.9 -10 -48 -25 73.1 69.2 63,6 Boiling Point C.) 760 883 705 357 800 733 746 74s 747 763 AH vaporization (cat/g.) 496 1,005 146 69.7 f 61a 226 189 247 264 292 Heat Capacity (cat/g.) 0.189 0. 31 0. 060 0. 0323 0. 212 0.088 0. 07 0. 095 0.10 0.11

(200 C.) (300 C.) AH Fusion (eat/g.) 14.6 27.1 3.766- 2.s 17. 5 6.28Y 4. 93 6.8 7.3 8 1 Density (gjm.) 0. 783 f 0. 891 1. 84 13.1 0.75 1. 27V 1. 80 1. 5s 1.53 1.50

(250 C.) (250 C.) (23 C.) (200 C.) Viscosity (centipoises) 0.26 0.38 0.3430 1.01 0.30 0.30 0.352 0.310. 0.303 0.311

` (250 o) (250 C.) (210.9 o.) (200 C.) Thermal Conductivity (ea1./see.em. 0. 10 0. 197 0. 044 0. 0303 0. 133 0. 072 0.080 0. 085 0. 087 0. 09s

C.) (300 o.) (200 o.) (at MP.) (220 C.).

Wt. Percent. Atom Percent Po1nt A B H A B H of this invention can be relatively light-weight because excessively high pressures are not involved. Furthermore, since cesium has a comparatively low 'boiling point, the temperatures encountered in this process are not such that excessive precautions are necessary to prevent the cesium vapor from attacking the equipment. When a turbine is used as the power producing means, it is possible to use a turbine having only two stages and a small rotor diameter to absorb `the enthalpy drop with cesium. This type of turbine is compact and lightweight which are important advantages `in missile, aircraft and spacecraft applications.

The ternary compositions of this :invention constitute highly desirable heat transfer media because of their relatively low melting and high boiling points coupled with good heat capacity and thermal-conductivity. The extremely low melting points of these alloys render them particularly desirable for use in applications in which it is impossible or impractical to maintain a heat transfer medium in a heated condition to prevent its solidification. The ternary mixtures of this invention are liquids having substantially constant physical and chemical properties over a temperature range of almost 800 C.

As will be understood by those skilled in the art, what has been described is the preferred embodiment of the invention; however, many modiiications, changes and substitutions can be made therein without departing from the scope and the spirit of the following claims:

What is claimed is:

1. The method comprising heating a ternary mixture of sodium, potassium and cesium to provide a stream of cesium rich vapor and a liquid residue, extracting energy from said vapor, condensing said cooled vapor to liquid cesium, admixing said liquid cesium with said liquid residue, the resulting mixture of said liquid cesium with said liquid residue having the composition of said ternary mixture.

2. The method comprising vaporizing a portion of a rst mixture of sodium, potassium and cesium to provide a stream of cesium rich vapor and a liquid residue, extracting energy from said vapor, condensing said vapor to a cesium rich liquid, admixing said cesium rich liquid with said liquid residue, the resulting mixture of said cesium rich liquid with said liquid residue having substantially the composition of said rst mixture, said first mixture containing from about 2 to about 7% sodium, from about 16 to about 36% potassium and from about to about 80% cesium.

3. Process for producing power which comprises: supplying a liquid mixture of sodium, potassium and cesium metals to a vaporizing zone, vaporizing a portion of said mixture in said zone to produce cesium-rich vapor-s and a cesium-lean liquid residue, employing said vapors to produce power, and thereafter condensing said vapors and combining the condensate with said residue to form said mixture.

4. Process for producing power which comprises: fractionating a ternary mixture of cesium, potassium and sodium metals to produce a cesium-rich vapor and a liquid binary mixture of potassium and sodium, employing said vapor to produce power, contacting said liquid with a source of heat to produce a heated liquid binary mixture, and condensing said vapor and combining the condensate with said heated binary mixture to form said ternary mixture.

References Cited by the Examiner UNITED STATES PATENTS 2,102,424 12/ 37 Larrecq 60--36 X 2,806,785 7/56 Doptoglon 75-134 X 2,911,297 11/59 Florenz 75-135 2,919,189 12/59 Nossen et al. 75-135 3,040,528 6/62 Tabor et al 60-36 3,095,698 7/63 Stern 60--36 IULIUS E. WEST, Primary Examiner.

DAVID L. RECK, EDGAR W. GEOGHEGAN,

Examiners. 

1. THE METHOD COMPRISING HEATING A TERNARY MIXTURE OF SODIUM, POTASSIUM AND CESIUM TO PROVIDE A STREAM OF CESIUM RICH VAPOR AND A LIQUID RESIDUE, EXTRACTING ENERGY FROM SAID VAPOR, CONDENSING SAID COOLED VAPOR TO LIQUID CESIUM, ADMIXING SAID LIQUID CESIUM WITH SALT LIQUID RESIDUE THE RESULTING MIXTURE OF SAID LIQUID CESIUM WITH SAID LIQUID RESIDUE HAVING THE COMPOSITION OF SAID TERNARY MIXTURE. 